1. Field of the Invention
The present invention relates to a method and a device for notifying a server failure recovery, and in particular to a method and a device for notifying a server failure recovery which notify a failure recovery of a server and the like to a client.
Recently, the Internet and an intranet have become widespread over all industrial fields and social systems including general homes. In the Internet and the intranet, a client can easily download information of text, graphic, image, voice, and the like from e.g. a web server and file information from an FTP (File Transfer Protocol) server.
In such an information transmission between the client and the server, when a failure occurs at the server, it is necessary to notify the occurrence and the recovery of the failure to the client.
2. Description of the Related Art
When a client tries to access a server by transmitting a packet requesting a connection (access) thereto and the server can not receive the packet due to a power disconnection or a failure occurrence on the server side, a router which transfers the packet to the server returns to the client a destination unreachable message of an ICMP (Internet Control Message Protocol) for giving an error notification and diagnosing a communication state.
This message allows the client to recognize that the connection request packet has not reached the server. However, the client or its operator can not recognize when the server, to which the access was tried, is powered up or the failure is recovered. Therefore, the client has been required to repeatedly transmit the connection request packet to the server with a time interval until the server is accessed.
When having tried but failed to access a web or an FTP server for browsing a web site or downloading a file, for example, a user is required to try to access the server again. This re-access operation is required to be performed until the server is accessed, which is a very troublesome operation for the user and causes an increase of a network load.
Also, when provided with an SNMP (Simple Network Management Protocol) agent function, the server can notify the startup of the server itself or the failure recovery to the SNMP manager side with the SNMP agent function. However, generally, only a network manager uses the SNMP manager, so that client's user, requiring to know the recovery state of the server most, does not know the fact until the notification from the network manager is obtained.
For solving this problem, in a method and a device for monitoring a client-server system disclosed in the Japanese Patent Application Laid-open No.2001-36552, the servers of two client-server systems operating on the same network respectively include a monitor.
The monitor of the server in one client-server system having detected a failure occurrence or a recovery thereof on the other client-server system notifies the failure or the recovery to the clients of its own client-server system.
Thus, it becomes possible for the monitor to notify the failure or the recovery of the counterpart client-server system to the clients of its own client-server system and for the clients having received the notification to avoid the repetition of a useless access to the server of the counterpart client-server system.
However, in this method and the device for monitoring the client-server system, the failure or the recovery of the system is not notified to the client of the client-server system in which the failure has occurred, requiring to know the failure/recovery state of the server most.
On the other hand, in a network system disclosed in the Japanese Patent Application Laid-open No. 2000-092054, a server has means to transmit the contents of a failure having occurred in the server itself or a failure recovery as a primary failure notification to the network.
Secondary notification means (e.g. a management terminal equipment) having received the primary failure notification notifies the failure occurrence or the failure recovery of the server to the client selected based on the received failure contents and a preset notifying destination client list per failure contents. Thus, it becomes possible to promptly give a failure recovery notification to the clients' users supposed to require to know the occurred failure most without troubling a system manager.
Thus, the method of giving the failure recovery notification, when the server has recovered from a failure, to all of the clients registered in the list is cumbersome because the recovery notification it to be transmitted to even a client which is not going to use the server, and has not been practical since the number of users to whom the failure recovery notification is transmitted becomes too large in an open server and the like which may be used by numerous persons.
Also, in a method and a device for controlling a server access in a client-server system disclosed in the Japanese Patent Application Laid-open No. 2000-188607, at least a single client having detected a failure of the server forms a representative client.
The representative client accepts standby client registration requests from other clients, and notifies the failure recovery notification of the server to the registered standby clients when the failure recovery of the server has been detected. Thus, the standby clients can start a communication with the server.
Thus, the method in which the representative client accepts the registration of the other standby client can eliminate the transmission of the failure recovery notification even to the client which does not try to use the server. However, in this method, the load of the representative client is increased, and additionally the client having tried but failed to access the server has to register itself in the representative client as a standby client.